The development within the windsurfing area is towards higher and more narrow sails, especially for funboards, which require higher masts, usually with an extension of the mast from previously 4.50 m to about 4.90 m, which can be achieved with a mast extender arranged at the lower end of the mast. Furthermore, new stiffer materials are used for the sails, such as "Kevlar" and "Mylar". Such new sails are less extensible and require the use of larger forces for stretching the sail along the mast and along the boom (fore or mast leech and boom leech).